Ground milling machines, which are employed, for example, for cold milling asphalt surfacing, stabilizing and/or recycling the underlying ground or also for the extraction of natural resources using so-called surface miners, usually comprise, as their essential elements, a machine frame with traveling devices, an operator platform, a drive engine and a milling device. The milling device includes a milling drum which has a rotation axis arranged horizontally and transversely to the working direction of the ground milling machine, and, rotating about its rotation axis, mills off the ground in working operation. The milling drum is usually arranged inside a so-called milling drum box, which is provided with a stripping plate that can be displaced upwards and downwards. In working or milling operation, when displaced downwards, i.e. in its stripping position, the bottom edge of the stripping plate rubs over the milled surface of the milling bed behind the milling drum and, in a position resting on the milling bed, scrapes milled material into the interior of the milling drum box. Provision may additionally be made here for the stripping plate to be actively pressed against the underlying ground from above with the aid of the adjusting device. The position of the stripping position, i.e. the extent to which the stripping plate is displaced downwards, decisively depends on the current milling depth of the ground milling machine. In alternative applications, it is also known to select the stripping position such that the stripping plate is not lowered onto the milling bed but is held at a defined height, usually a few centimeters, to leave a defined amount of milled material on the milling bed. For transport travels and/or for maintenance purposes, it is possible to elevate the stripping plate in vertical direction into a transport position. It is also known to additionally design the stripping plate such that it can be swiveled open, for example from the elevated transport position, for maintenance of the milling drum. Relevant prior art arrangements are described, for example, in DE 10 2013 015 873 A1, DE 10 2015 002 426 A1, DE 10 2012 012 607 A1, DE 10 2012 018 918 A1 and DE 10 2013 006 105 A1. Further, it is known to provide a ground milling machine with sensors for the detection of wear at chisels.
With such ground milling machines, it may happen during the working or milling process that the stripping plate rubbing over the milling bed gets stuck, in the working or milling direction, at edges, small steps, grooves or the like that are present on the underlying ground to be processed and protrude vertically and/or laterally into the area of the milling bed. In the case of such a “getting stuck” event, there is the risk that the stripping plate gets overloaded and a halt of the ground milling machine is initiated or caused, which is not desired or expected by the operator of the ground milling machine. This may even result in damage to the entire machine.
In the prior art, two approaches are known so far for avoiding such a halt due to the stripping plate “getting stuck” at obstacles in or at the underlying ground to be processed. According to a first approach, the driver or operator of the ground milling machine has to recognize the stall of the ground milling machine by himself and then elevate or lift the stripping plate through manual actuation in order to be able to circumvent or travel over the obstacle. Then, once the obstacle, or at least the beginning of the obstacle, has been overcome, the operator has to lower the stripping plate back to the working position, which again needs to be done manually. Since each operator has a different responsiveness and further an experienced milling machine driver is required for this, there may be large differences in the subjective recognition and classification of the obstacle. Damage cannot be avoided reliably. According to a second approach, the lowermost edge of the stripping plate has spring-loaded strips arranged thereon, which when striking against an obstacle in the horizontal direction “deflect inwards” and through their position change send a sensor signal to the machine control. This signal is used to automatically lift the stripping plate and shortly thereafter return it to the initial state, i.e. to the floating position. The contact strips thus act as a type of pushbutton which is essentially activated directly by the obstacle. This variant involves a complex design to provide the spring-loaded strips, which results in high costs. Moreover, this system has a relatively high susceptibility to errors and failure.